P. Sreekumar

Publication List Details

Period

1993 - 2008

Number

49

Co-Authors

Gamma-ray luminosity function of Gamma-ray bright AGNs (2008)

Bhattacharya, D., Sreekumar, P., Mukherjee, R.

Detection of Gamma-ray emission from a class of active galactic nuclei (viz blazars), has been one of the important findings from the Compton Gamma Ray Observatory (CGRO). However, their Gamma-ray...

Does the Blazar Gamma-Ray Spectrum Harden with Increasing Flux? Analysis of 9 Years of EGRET Data (2007)

Nandikotkur, Giridhar, Jahoda, Keith M., Hartman, R. C., Mukherjee, R., Sreekumar, P., Böttcher, M., ...

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO) discovered gamma-ray emission from more than 67 blazars during its 9 yr lifetime. We conducted an...

ASTROSAT observations: complementary studies from ground (2005)

Sreekumar, P

Since the advent of the satellite era, X-ray astronomy and UV astronomy have advanced tremendously. The discovery of intense X-ray emission from accreting compact objects has permitted very detailed...

X-ray spectral evolution of low-mass X-ray binary GX 349+2 (2003)

Agrawal, V. K., Sreekumar, P.

We present the results of a systematic investigation of spectral evolution in the Z source GX 349+2, using data obtained during 1998 with Proportional-Counter-Array (PCA) on-board the RXTE satellite....

EGRET upper limits on the high-energy gamma-ray emission of galaxy clusters (2003)

Reimer, O., Pohl, M., Sreekumar, P., Mattox, J. R.

We report EGRET upper limits on the high-energy gamma-ray emission from clusters of galaxies. EGRET observations between 1991 and 2000 were analyzed at positions of 58 individual clusters from a...

The Gamma Ray Burst experiment on the Indian SROSS C-2 satellite (2001)

Sinha, S, Sreekumar, P, Kasturirangan, K

The SROSS C-2 satellite launched by the ASLV carried aloft a CsI gamma ray burst detector. To date, 51 GRB events have been detected unambiguously with 22 being common with BATSE. The experiment with...

What can GLAST say about the origin of cosmic rays in other galaxies ? (2000)

Digel, S. W., Moskalenko, I. V., Ormes, J. F., Sreekumar, P., Williamson, R.

Gamma rays in the band from 20 MeV to 300 GeV, used in combination with data from radio and X-ray bands, provide a powerful tool for studying the origin of cosmic rays in our sister galaxies...

RXTE Observations of PKS 2155-304 during the November 1997 Gamma-Ray Outburst (1999)

Vestrand, W. T., Sreekumar, P.

We present x-ray observations of the nearby BL Lac PKS 2155-304 taken when it was undergoing a GeV/TeV gamma-ray outburst. During the outburst we measured x-ray fluxes in the 2-10 keV band that are...

GeV emission from the nearby radio galaxy Centaurus A (1999)

Sreekumar, P., Bertsch, D. L., Hartman, R. C., Nolan, P. L., Thompson, D. J.

EGRET has detected 67 sources associated with active galactic nuclei. With the exception of radio galaxy Cen A, all are classified as belonging to the blazar class of active galactic nuclei. The...

Broadband Spectral Analysis of PKS 0528+134: A Report on Six Years of EGRET Observations (1999)

Mukherjee, R., Boettcher, M., Hartman, R. C., Sreekumar, P., Thompson, D. J., Mahoney, W. A., ...

The multiwavelength spectra of PKS 0528+134 during six years of observations by EGRET have been analyzed using synchrotron self-Compton (SSC) and external radiation Compton (ERC) models. We find that...

The Third Egret Catalog of High-Energy Gamma-Ray Sources (1999)

Hartman, R. C., Bertsch, D. L., Bloom, S. D., Chen, A. W., Deines-Jones, P., Esposito, J. A., ...

The third catalog of high-energy gamma-ray sources detected by the EGRET telescope on the Compton Gamma Ray Observatory includes data from 1991 April 22 to 1995 October 3 (cycles 1, 2, 3, and 4 of...

The Third Egret Catalog of High-Energy Gamma-Ray Sources (1999)

Hartman, R. C., Bertsch, D. L., Bloom, S. D., Chen, A. W., Deines-Jones, P., Esposito, J. A., ...

The third catalog of high-energy gamma-ray sources detected by the EGRET telescope on the Compton Gamma Ray Observatory includes data from 1991 April 22 to 1995 October 3 (cycles 1, 2, 3, and 4 of...

A Study of High Energy Emission from the TeV blazar Mrk 501 during Multiwavelength Observations in 1996 (1998)

Kataoka, J., Mattox, J. R., Quinn, J., Kubo, H., Makino, F., Takahashi, T., ...

We present the results of a multiwavelength campaign for Mrk 501 performed in March 1996 with ASCA, EGRET, Whipple, and optical telescopes. In the X-ray band, a spectral break was observed around 2...

P. L. Nolan (1998)

P. L. Nolan, D. L. Bertsch, B. L. Dingus, J. A. Esposito, C. E. Fichtel, J. M. Fierro, ...

The EGRET instrument aboard the Compton Gamma Ray Observatory (CGRO) has completed the first all-sky survey in high-energy gamma rays and has repeatedly viewed selected portions of the sky. Analysis...

The Extragalactic Diffuse Gamma-Ray Emission (1997)

P. Sreekumar, F. W. Stecker

The all-sky surveys in fl-rays by the imaging Compton telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton GammaRay Observatory for the first time allows...

EGRET Observations of the Extragalactic Gamma Ray Emission (1997)

Sreekumar, P.

The all-sky survey in high-energy gamma rays (E$>$30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to...

The Extragalactic Diffuse Gamma-Ray Emission (1997)

Sreekumar, P., Stecker, F. W., Kappadath, S. C.

The all-sky surveys in gamma-rays by the imaging Compton telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory for the first time...

The Extragalactic Diffuse Gamma-Ray Emission (1997)

P. Sreekumar, F. W. Stecker

. The allsky surveys in fl-rays by the imaging Compton telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory for the first time...

Constraints from Undetected Gamma-Ray Sources (1997)

C. E. Fichtel, P. Sreekumar

. The number of positive gamma-ray source detections by the Compton Gamma-Ray Observatory has been large, and the significance of the results has been substantial, as is described in other reports at...

A spectral study of gamma-ray emitting AGN (1997)

Pohl, M., Hartman, R. C., Jones, B. B., Sreekumar, P.

In this paper we present a statistical analysis of the gamma-ray spectra of flat-spectrum radio quasars (FSRQ) compared to those of BL Lacs. The average spectra and possible systematic deviations...

Possible EGRET Gamma-Ray Burst Detection Independent of BATSE Triggering (1996)

B. B. Jones, D. L. Bertsch, B. L. Dingus, J. E. Esposito, C. E. Fichtel, J. M. Fierro, ...

EGRET spark chamber data collected between 1991 April 22 and 1994 August 29 have been analyzed for gamma-ray burst events independent of BATSE triggering. To date, five gamma-ray bursts that are...

P. L. Nolan (1995)

P. L. Nolan, D. L. Bertsch, B. L. Dingus, J. A. Esposito, C. E. Fichtel, J. M. Fierro, ...

The EGRET instrument aboard the Compton Gamma Ray Observatory (CGRO) has completed the first all-sky survey in high-energy gamma rays and has repeatedly viewed selected portions of the sky. Analysis...

Observation of High-Energy Gamma Rays from the QSO CTA 102 (1995)

P. L. Nolan, D. L. Bertsch, C. E. Fichtel, R. C. Hartman, S. D. Hunter, G. Kanbach, ...

The quasar CTA 102 (QSO 2230+114) was observed four times in 1991-1992 by the EGRET high-energy gamma ray telescope on the Compton Gamma Ray Observatory satellite. In the 1992 January 23 -- February...

The Unidentified Gamma Ray Source Gro J1837+59 (1995)

P. L. Nolan, J. M. Fierro, Y. C. Lin, P. F. Michelson, T. D. Willis, J. Chiang, ...

The EGRET gamma-ray telescope has detected a persistent source of highenergy gamma rays which has not been identified. It was detected in seven different observations in 1991--1993. Variations in the...

Performance of the EGRET Astronomical Gamma Ray Telescope (1995)

P. L. Nolan, D. L. Bertsch, C. E. Fichtel, R. C. Hartman, R. Hofstadter, E. B. Hughes, ...

On April 5, 1991, the Space Shuttle Atlantis carried the Compton Gamma Ray Observatory (CGRO) into orbit, deploying the satellite on April 7. The EGRET instrument was activated on April 15, and the...

Possible EGRET Gamma-Ray Burst Detection Independent of BATSE Triggering (1970)

B. B. Jones, D. L. Bertsch, B. L. Dingus, J. E. Esposito, C. E. Fichtel, J. M. Fierro, ...

EGRET spark chamber data collected between 1991 April 22 and 1994 August 29 have been analyzed for gamma-ray burst events independent of BATSE triggering. To date, five gamma-ray bursts that are...